[cft] subreg validation round 2

[Kaz Kojima]

Richard Henderson <rth@redhat.com> wrote:
> This passes on i686, alpha, ia64, powerpc linux, and sparc-solaris.
> Given Ulrich's previous testing, it *ought* to pass on s390.  Any
> other takers before I check it in and have to pick up pieces after
> the fact?

FYI, bootstrapped successfully on sh4-unknown-linux-gnu.  The native
regtest hasn't completed yet, though there are no regressions on x86
cross sh4-unknown-linux-gnu.

Regards,
	kaz